now that i know a bit more from your description here, it is always a good idea to run 20% for that extra little bit of protection, and as far as i know, you aren't supposed to run 2 strokes on 18%, i amn pretty sure they need at least 20%. if it was leaning out for 1-2 mins, and running on an unacceptably low oil precentage anyway, i think you have definatly trashed it. i don't mean to sound critical, but put in your cheapest plane, because i wouldn't rely on it, and it will probably not last the 20 years or so that these engines are known to last. if i were you, switch IMMEDIATLY to 20% if you want that engine to ever run nicely again. i am not sure what you guys do to your engines, but i've got an infinate idle on that engine. i have it in my trainer, so it doesn't matter much anyway, but it won't die unless it runs dry or i kill it